title: Radiological assessment of mesenteric and retroperitoneal cysts in adults: is there a role for chemical shift MRI?
abstract: OBJECTIVE
  The purpose of this study was to assess the potential role for chemical shift magnetic resonance imaging (MRI) in identifying lymphangiomas from other cystic mesenteric and retroperitoneal masses.
  
  
  METHODS
  A retrospective search of radiology database identified 24 consecutive patients with mesenteric and retroperitoneal cysts (nine men, 15 women; mean age, 41 years; age range, 19-75 years) who had undergone MR which included in-phase and opposed-phase chemical shift imaging. Signal intensity (SI) decrease between in-phase and opposed-phase MR images of the cyst was evaluated qualitatively by two radiologists. Ultrasound (US), computed tomography (CT), and MRI findings of the morphological appearances of all the cystic lesions that demonstrated significant signal drop on chemical shift MR were also recorded.
  
  
  RESULTS
  Of mesenteric and retroperitoneal cysts, 33% (8/24) revealed qualitative decrease in intensity on opposed-phase MR images relative to that seen on in-phase images. On ultrasound, these cysts demonstrated anechoic simple fluid. Their mean CT attenuation was 13 HU (range: 5-20 HU). Signal loss on fat-suppressed T1-weighted sequences was displayed only by a single cyst. None of the lesions with qualitative SI decrease on opposed-phase MR showed suggestion of lipid on US and CT.
  
  
  CONCLUSIONS
  The presence of intra cystic lipid detected by chemical shift MR may not be overt on cross-sectional imaging such as US and CT. Chemical shift MRI provides additional sensitivity and specificity as an imaging test for demonstration of lipid within mesenteric and retroperitoneal cysts enabling a higher diagnostic yield for lymphangioma leading to more appropriate patient management.
authors.affiliation: Abdominal Imaging Division, Joint Department of Medical Imaging, University Health Network, Mount Sinai Hospital and Women's College Hospital, University of Toronto, Toronto, Canada. anoop.ayyappan@ttuhsc.edu
authors.forename: Anoop P
authors.initials: AP
authors.lastname: Ayyappan
authors.forename: Kartik S
authors.initials: KS
authors.lastname: Jhaveri
authors.forename: Masoom A
authors.initials: MA
authors.lastname: Haider
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000032:analysis; D005260:Female; D006801:Humans; D008055:Lipids / Q000032:analysis*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008639:Mesenteric Cyst / Q000175:diagnosis* / Q000378:metabolism; D008875:Middle Aged; D015203:Reproducibility of Results; D012187:Retroperitoneal Space / Q000473:pathology*; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D015415:Biomarkers; D008055:Lipids